Technical Field
The present application relates to compositions and devices for energy storage and distribution. The compositions comprise a plurality of lead particles and a plurality of carbon particles and exhibit desirable electrochemical properties suitable for use in hybrid carbon-lead energy storage devices.
Description of the Related Art
Hybrid energy storage devices, also known as asymmetric supercapacitors or hybrid battery/supercapacitors, utilize a combination of battery electrodes and supercapacitor electrodes. For example, hybrid lead-carbon energy storage devices employ lead-acid battery positive electrodes (cathodes) and ultracapacitor negative electrodes (anodes). Such devices comprise a unique set of characteristics including long cycle life, increased power, fast recharge capability and a wide range of temperature operability.
Conventional lead-acid energy storage devices may have limited active life and power performance. Hybrid energy storage devices employing either carbon or lead-acid electrodes (but not their combination at the same electrode) may provide some improvement and advantages over conventional lead-acid devices; however, their active life, energy capacity and power performance can likewise be limited. For example, lead-based positive electrodes often fail due to a loss of active lead dioxide paste from the current collector grid after multiple charge/discharge cycles. The anodes of these devices also deteriorate upon multiple charge/discharge cycles because the discharge lead sulfate crystal size increases and leads to ‘densification’ of the negative plate resulting in reduced charge acceptance and loss of capacity. This electrode failure is thought to be a result of secondary and tertiary side reactions caused by impurities in the carbon materials employed in these devices. In addition, the low surface area of the electrodes and relatively high ion migration distances limits the power performance of these devices.
The conventional wisdom is that such energy storage devices, particularly those made in commercial quantities require significant compression of the electrodes as they are placed into the case for the energy storage device. Moreover, because supercapacitor energy storage devices of the sort discussed herein comprise lead-based positive electrodes together with carbon-based negative electrodes, and lead-based positive electrodes are known from the lead acid battery art, considerable attention has been paid to the development of improved negative electrodes.
The positive electrode of ultracapacitor energy storage devices effectively defines the active life of the device. The negative electrodes typically will not wear out; but on the other hand, just as with lead acid storage batteries, the positive lead-based electrodes of ultracapacitor energy storage devices will typically fail first. Those failures are generally the result of the loss of active lead dioxide paste shedding from the current collector grid as a consequence of spalling and dimensional change deterioration during charging and discharging cycles.
Although the need for improved carbon materials for use in hybrid lead-carbon energy storage devices has been recognized, such carbon material has yet to be developed. Accordingly, there continues to be a need in the art for improved electrode materials for use in hybrid lead-carbon electrical energy storage devices, as well as for methods of making the same and devices containing the same. The present invention fulfills these needs and provides further related advantages.